class Vehicle:
    def __init__(self, speed):
        self.speed = speed

    def drive(self, distance):
        print("need %f hour(s)" %(distance / self.speed))

class Bike(Vehicle):
    pass

class Car(Vehicle):
    def __init__(self, speed, fuel):
        Vehicle.__init__(self, speed)
        self.fuel = fuel

    def drive(self, distance):
        Vehicle.drive(self, distance)
        print("need %f fuels" %(distance * self.fuel))

b = Bike(15.0)
c = Car(80.0, 0.012)
b.drive(100.0)
c.drive(100.0)
